In the fields of medicine and clinical chemistry, many studies and determinations of physiologically reactive species such as cells, proteins, enzymes, cofactors, nucleic acids, substrates, antigens, antibodies, and so forth are carried out using conjugates involving specific binding pair members or labels or the like. Various assay techniques that involve the binding of specific binding pair members are known. These assay techniques generally also involve a label used in the detection part of the assay.
Polysaccharides, particularly dextran, have been conjugated to specific binding pair members, for example, to increase the stability of the specific binding pair member. In some approaches, a polysaccharide is bound to a surface of a support and a specific binding pair member is linked to the polysaccharide to provide a surface coated with polysaccharide and having a specific binding pair member attached thereto. Such supports are employed in assays for analytes. conjugation of specific binding pair members to polysaccharides increases the bulkiness of these molecules, which can enhance their effectiveness in assays involving specific binding pair members by interfering with binding to complementary specific binding pair members. Additionally, these conjugates, when present on a surface, permit specific binding of a complementary specific binding pair member to the surface with reduced non-specific binding. The polysaccharide conjugates are employed in numerous types of assays, including homogeneous and heterogeneous assays and so forth, which are performed on biological samples such as blood, serum, and the like.
There are, however, certain samples such as, for example, serum samples, which produce a positive result independently of the presence or absence of an analyte in assays in which the aforementioned polysaccharide coated supports are employed. The likely explanation for this result is the non-specific binding of components from the sample to one or more of the assay reagents particularly the polysaccharide coated support with linked specific binding pair member. The non-specific binding can increase the reading of a positive test result, and in some instances, the non-specific binding can produce a positive reading when the analyte is absent, either case providing a misleading assay result.
One approach has been suggested for nonspecific IgG binding to a polymeric solid phase in an immunoassay of a serum sample. The approach involves the inclusion of a water-soluble polymer in the liquid phase where the water-soluble polymer is formed by polymerization of monomers that are the same as, or have approximately the same immunological binding affinity as, monomers of the polymer at the solid phase surface. Materials employed as the water soluble polymer included poly(styrene-alt-maleic acid) and poly(acrylic acid), which demonstrated superiority over poly(methacrylic acid) and dextran and a number of other materials.
There remains a need for agents for blocking non-specific binding in assays involving polysaccharide conjugates linked to a support.